Determination of δ13C Values of Apple and Apple Juice Concentrate by the Stable Isotopes Ratio-Mass Spectrometry

The reference standard selected is traceable to the CRM of olive oil ［Cat. No.B 2172, Batch 3130, with its δ13C value (vs. PDB) of (-28.51±0.16)‰］ obtained from IAEA and the stable isotopes ratio mass spectrometry was used for the determination of δ13C of apple pulp and apple juice, on the base of which the range of δ13C values of apples produced in our country was determined and the quality of apple juice produced was appraised. The apple sample was peeled and the pulp was sliced and made into paste. After centrifuging, the supernatant was taken and heated at 75 ℃ for 2-3 h to condense it to a syrupy state, having its Brix degree of about 70. In general, the sample of apple juice concentrate was in syrupy state and having its Brix degree of around 70. Two μL of either of the above samples, as well as 2 μL of the olive oil standard were taken and placed in tin cups separately for MS analysis. Values of ratio of the stable isotopes of 13C and 12C were substituted into the given formula and the values of δ13C were calculated. Precision was tested and values of RSD′s (n=11) obtained were all less than 0.021%. The range of δ13C values for apples grown in various origin in our country was between -29.17‰ and -23.33‰.